Scoping Studies to Determine Impact of a Low-Alkali Phase Separated Frit on the Behavior of the Frit Slurry and Slurry Mix Evaporator Rheology
- Savannah River Site (SRS), Aiken, SC (United States); Savannah River National Laboratory (SRNL), Aiken, SC (United States)
The frits used in the vitrification process at the Defense Waste Processing Facility (DWPF) are alkali borosilicate glasses, which are composed mainly of B2O3, alkali (Li2O and Na2O) and SiO2. As the total alkali concentration in a borosilicate glass is reduced, liquid-liquid immiscibility is exhibited by the glassforming melt, which is analogous to the behavior of oil and water. Upon cooling, the resulting glass matrix is said to be phase separated. The immiscible region is controlled by both composition and temperature. Viscosity of the melt is also a factor as it impacts the reaction rate (kinetics) of phase separation. The reaction rate (kinetics) leading to phase separation is slow for higher viscosity melts, and if such a melt is cooled rapidly (e.g., quenched in water), the resulting glass could be homogeneous, or the scale of the phase separated microstructure could be of no practical significance. Phase separated alkali borosilicate glasses tend to form a more durable silica-rich phase and a less durable alkali borate-rich phase. The overall durability of the phase separated glass depends on the morphology (physical arrangements) of each of these phases. For example, droplets of the alkali borate-rich phase may form within a silicate rich matrix, which would be a more durable glass than a glass with an interconnected alkali borate-rich phase.
- Research Organization:
- Savannah River National Laboratory (SRNL), Aiken, SC (United States); Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- AC09-08SR22470
- OSTI ID:
- 1527157
- Report Number(s):
- SRNL-STI-2019-00152
- Country of Publication:
- United States
- Language:
- English
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